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Date: Tue, 2 Jul 2019 16:06:30 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Anshuman Khandual <anshuman.khandual@arm.com>
Subject: Re: [PATCH V2] mm/ioremap: Probe platform for p4d huge map support
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Cc: Stephen Rothwell <sfr@canb.auug.org.au>, x86@kernel.org,
 Peter Zijlstra <peterz@infradead.org>,
 Catalin Marinas <catalin.marinas@arm.com>,
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 Andy Lutomirski <luto@kernel.org>, Thomas Gleixner <tglx@linutronix.de>,
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 "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
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On Fri, 28 Jun 2019 10:50:31 +0530 Anshuman Khandual <anshuman.khandual@arm.com> wrote:

> Finishing up what the commit c2febafc67734a ("mm: convert generic code to
> 5-level paging") started out while levelling up P4D huge mapping support
> at par with PUD and PMD. A new arch call back arch_ioremap_p4d_supported()
> is being added which just maintains status quo (P4D huge map not supported)
> on x86, arm64 and powerpc.

Does this have any runtime effects?  If so, what are they and why?  If
not, what's the actual point?